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24 Jun 2002

Volume 80, Issue 25, pp. 4687-4873

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Measuring thin film and multilayer elastic constants by coupling in situ tensile testing with x-ray diffraction

K. F. Badawi, P. Villain, Ph. Goudeau, and P.-O. Renault

Appl. Phys. Lett. 80, 4705 (2002); http://dx.doi.org/10.1063/1.1488701 (3 pages) | Cited 28 times

Online Publication Date: 17 June 2002

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A direct determination of the Young’s modulus and the Poisson’s ratio in a 140 nm polycrystalline tungsten thin film deposited by ion-beam sputtering on a polyimide substrate has been performed by coupling x-ray diffraction measurements with in situ tensile testing. The method described in this article to extract the Young’s modulus of thin films from the evolution of the sin2 ψ curves as a function of applied load only requires to know the substrate Young’s modulus. The determination of the thin film Poisson’s ratio can be realized without knowing any of the substrate elastic constants. In the case of the tungsten thin film, the obtained Young’s modulus was close to the bulk material one whereas the Poisson’s ratio was significantly larger than the bulk one. © 2002 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
68.65.Cd Superlattices
62.20.D- Elasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations
81.70.Bt Mechanical testing, impact tests, static and dynamic loads

Suppression of quasicrystallization by nonlinear viscous flow in Zr–Al–Ni–Cu–Pd glassy alloys

J. Saida, S. Ishihara, H. Kato, A. Inoue, and H. S. Chen

Appl. Phys. Lett. 80, 4708 (2002); http://dx.doi.org/10.1063/1.1488689 (3 pages) | Cited 11 times

Online Publication Date: 17 June 2002

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The quasicrystallization at the initial stage under viscous flow at 673 K (20 K above the glass transition temperature) was investigated in a Zr65Al7.5Ni10Cu12.5Pd5 bulk glassy alloy. The compressive deformation at strain rates of 2×10−3 s−1 and 1×10−2 s−1 was subjected to the bulk glassy alloy for 60 s followed by the preannealing for 120 s for thermal equilibration in an Ar atmosphere. The glass undergoes Newtonian and non-Newtonian flow at the strain rates of 2×10−3 s−1 and 1×10−2 s−1, respectively. The linear viscous flow brings a significant decrease in the first exothermic peak in the differential scanning calorimetry (DSC) curve corresponding to the transformation from glassy to icosahedral phase, but is identical to that in the reference sample annealed for 180 s at 673 K without deformation. However, the number of icosahedral particles in the transmission electron microscopy image as well as the decrease of the first exothermic peak in the DSC curve in the nonlinear viscous flow is much less as compared with those in the linearly deformed and reference samples. These results indicate the suppression of the transformation from the glassy to icosahedral phase by the nonlinear viscous flow. The suppression of the transformation is suggested to be originated from the retardation of the growth by the stress-induced disordered atomic configuration in the glassy state during the nonlinear viscous flow. © 2002 American Institute of Physics.
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61.44.Br Quasicrystals
62.20.F- Deformation and plasticity
81.40.Lm Deformation, plasticity, and creep
61.43.Fs Glasses

Temperature dependence of the absorption saturation relaxation time in light- and heavy-ion-irradiated bulk GaAs

J. Mangeney, N. Stelmakh, F. Aniel, P. Boucaud, and J.-M. Lourtioz

Appl. Phys. Lett. 80, 4711 (2002); http://dx.doi.org/10.1063/1.1489086 (3 pages) | Cited 14 times

Online Publication Date: 17 June 2002

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The absorption saturation relaxation time in light- and heavy-ion-irradiated GaAs saturable absorbers has been measured as a function of the temperature in the range from 7 to 300 K. For both types of samples, the relaxation time is shorter than 4 ps at 7 K. A regular increase of this time with temperature is observed for light-ion-irradiated samples, a value of 9.5 ps being reached at room temperature. In contrast, an almost temperature-independent relaxation time is found for heavy-ion-irradiated samples. The results are interpreted on the basis of a simplified relaxation model accounting for capture and emission from defect levels. We suggest that light-ion irradiation creates shallow centers whereas heavy-ion irradiation creates deep centers. © 2002 American Institute of Physics.
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42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
71.55.Eq III-V semiconductors

Height-controlled InAs quantum dots by using a thin InGaAs layer

Jin Soo Kim, Phil Won Yu, Joo In Lee, Jong Su Kim, Song Gang Kim, Jae-Young Leem, and Minhyon Jeon

Appl. Phys. Lett. 80, 4714 (2002); http://dx.doi.org/10.1063/1.1489484 (3 pages) | Cited 14 times

Online Publication Date: 17 June 2002

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The structural and optical properties of height-controlled InAs quantum dots (QDs) have been investigated by transmission electron microscopy (TEM) and photoluminescence (PL). By depositing 1.4 nm In0.15Ga0.85As and a 1 monolayer (ML) InAs layer with different periods on 3 ML InAs QDs, the height of InAs QDs was systematically controlled with similar lateral size. In TEM images, the indication of dislocations due to the large strain, which can be easily seen in large QDs, is not observed even for the QD sample with the highest aspect ratio (height/width). The PL peak position is shifted toward the longer wavelength with an increase in the aspect ratio of QDs. As the aspect ratio is increased, the full width at half maximum in PL measured at 10 K is decreased from 71 to 34 meV indicating that the inhomogeneous broadening caused by the fluctuation in QD size, especially the height, is significantly reduced. © 2002 American Institute of Physics.
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68.65.Hb Quantum dots (patterned in quantum wells)
78.67.Hc Quantum dots
78.55.Cr III-V semiconductors
61.72.Lk Linear defects: dislocations, disclinations

Far-infrared stimulated emission from optically excited bismuth donors in silicon

S. G. Pavlov, H.-W. Hübers, M. H. Rümmeli, R. Kh. Zhukavin, E. E. Orlova, V. N. Shastin, and H. Riemann

Appl. Phys. Lett. 80, 4717 (2002); http://dx.doi.org/10.1063/1.1489080 (3 pages) | Cited 30 times

Online Publication Date: 17 June 2002

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Far-infrared stimulated emission from optically pumped neutral Bi donors in silicon has been obtained. Lasing with wavelengths of 52.2 and 48.6 μm from the intra-center 2p±→1s(E:Γ8),1s(T2:Γ8) transitions has been realized under CO2 laser pumping. The population inversion mechanism is based on fast optical-phonon-assisted relaxation from the 2p0 and 2s excited states directly to the ground 1s(A) state leading to relatively small population in the intermediate 1s(E), 1s(T2) excited states. © 2002 American Institute of Physics.
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78.45.+h Stimulated emission
42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.50.-p Quantum optics
71.55.Cn Elemental semiconductors

Suppression of interfacial atomic diffusion in InGaNAs/GaAs heterostructures grown by molecular-beam epitaxy

C. S. Peng, E.-M. Pavelescu, T. Jouhti, J. Konttinen, I. M. Fodchuk, Y. Kyslovsky, and M. Pessa

Appl. Phys. Lett. 80, 4720 (2002); http://dx.doi.org/10.1063/1.1488687 (3 pages) | Cited 20 times

Online Publication Date: 17 June 2002

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We have studied the effects of annealing of InGaNAs/GaAs heterostructures on diffusion at the interfaces and the resultant changes in optical and structural properties. Interdiffusion between In and Ga was found to be very significant. Inserting a thin compressively strained layer of InxdGa1−xdNydAs1−yd on either side of an InxqGa1−xqNyqAs1−yq quantum well (QW) suppressed this interdiffusion significantly. As a consequence, a blue shift of the photoluminescence signal after annealing remained small and the optical activity was largely improved. It was also found that a small amount of N incorporated in InGaAs QWs embedded in GaAs increased the In/Ga interdiffusion and that increased mechanical stresses enhanced the interdiffusion. © 2002 American Institute of Physics.
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78.67.De Quantum wells
78.55.Cr III-V semiconductors
66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation
61.72.Cc Kinetics of defect formation and annealing
78.20.Ek Optical activity

Probing strained InGaN/GaN nanostructures with ultrashort acoustic phonon wave packets generated by femtosecond lasers

J. S. Yahng, Y. D. Jho, K. J. Yee, E. Oh, J. C. Woo, D. S. Kim, G. D. Sanders, and C. J. Stanton

Appl. Phys. Lett. 80, 4723 (2002); http://dx.doi.org/10.1063/1.1488693 (3 pages) | Cited 21 times

Online Publication Date: 17 June 2002

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Large amplitude time-domain oscillations are detected in InxGa1−xN/GaN structures via femtosecond differential reflectivity spectroscopy. The oscillation amplitude increases with increasing indium fraction and abruptly disappears at a critical time that depends on GaN thickness. We show that spatially localized, coherent acoustic phonon wave packets are generated via the photoexcited carriers and propagate into the samples modulating the reflectivity. Our results show that a system with strong built-in strain can be a very effective source for ultrafast acoustic phonon wave packets which can be used as a powerful probe for nanoscale structures. © 2002 American Institute of Physics.
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63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
81.07.Bc Nanocrystalline materials
78.47.-p Spectroscopy of solid state dynamics
78.66.Fd III-V semiconductors
61.46.-w Structure of nanoscale materials
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters

Origin of the split Si–H stretch mode on hydrogen terminated 6H-SiC(0001): Titration of crystal truncation

N. Sieber, T. Stark, Th. Seyller, L. Ley, C. A. Zorman, and M. Mehregany

Appl. Phys. Lett. 80, 4726 (2002); http://dx.doi.org/10.1063/1.1488692 (3 pages) | Cited 12 times

Online Publication Date: 17 June 2002

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Using Fourier-transform infrared absorption spectroscopy, we have studied the Si–H stretch mode on hydrogenated 6H-SiC(0001) and 3C-SiC(111). On 6H-SiC(0001) two signals at 2133.5 and 2128.0 cm−1 are observed. Their intensity ratio varies with sample preparation temperature. On 3C-SiC(111) essentially a single mode is observed at 2128.4 cm−1 at all temperatures. The origin of the two modes is explained in terms of different stacking arrangement below the surface. The possibility for a stacking rearrangement during the hydrogen treatment is discussed. © 2002 American Institute of Physics.
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68.35.Ja Surface and interface dynamics and vibrations
78.30.Hv Other nonmetallic inorganics
81.65.-b Surface treatments

Cation substituted (Ca2CoO3)xCoO2 films and their thermoelectric properties

Ichiro Matsubara, Ryoji Funahashi, Masahiro Shikano, Kei Sasaki, and Hiroyuki Enomoto

Appl. Phys. Lett. 80, 4729 (2002); http://dx.doi.org/10.1063/1.1489706 (3 pages) | Cited 17 times

Online Publication Date: 17 June 2002

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We have controlled in-plane stress in the CoO2 sublattice of (Ca2CoO3)xCoO2 by cationic substitution of alkaline earth metals at the Ca site. The effects of the magnitude of the stress on thermoelectric properties have been investigated by using highly grain-oriented polycrystalline thin films. The in-plane compressive stress is released by the partial substitution of Sr for Ca. With increasing in-plane stress, the magnitude of thermoelectric power and resistivity increased. © 2002 American Institute of Physics.
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73.50.Lw Thermoelectric effects
68.60.Bs Mechanical and acoustical properties
73.61.Le Other inorganic semiconductors
72.20.Pa Thermoelectric and thermomagnetic effects
72.20.Fr Low-field transport and mobility; piezoresistance

NbO2F: An oxyfluoride phase with wide band gap and electrochromic properties

Hiroshi Mizoguchi, Masahiro Orita, Masahiro Hirano, Satoru Fujitsu, Tomonari Takeuchi, and Hideo Hosono

Appl. Phys. Lett. 80, 4732 (2002); http://dx.doi.org/10.1063/1.1489703 (3 pages) | Cited 3 times

Online Publication Date: 17 June 2002

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It was demonstrated that the oxyfluoride NbO2F with an ReO3-type structure is a promising electrochromic material with wide band gap. Measurement of diffuse reflectance spectra revealed the optical band gap of NbO2F (∼3.1 eV) to be wider than that of WO3 (∼2.6 eV). It was rendered electron conductive by heating at 770 K in the presence of Pt powder in H2. Electrical conductivity for the blue-colored sintered sample of NbO2F obtained was 6×10−3 S cm−1 at 300 K, and a temperature dependence showed the semiconductive behaviors. A reversible electrochromism between pale-blue and deep-blue-color was found in H2SO4 and Na2SO4 aqueous solution. © 2002 American Institute of Physics.
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78.20.Jq Electro-optical effects
72.20.Fr Low-field transport and mobility; piezoresistance
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.40.Fy Semiconductors
72.80.Jc Other crystalline inorganic semiconductors

Synthesis route-dependent formation of quasicrystals in Zr70Pd30 and Zr70Pd20Cu10 amorphous alloys

D. J. Sordelet, E. Rozhkova, M. F. Besser, and M. J. Kramer

Appl. Phys. Lett. 80, 4735 (2002); http://dx.doi.org/10.1063/1.1488686 (3 pages) | Cited 11 times

Online Publication Date: 17 June 2002

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The devitrification of mechanically milled amorphous Zr70Pd30 and Zr70Pd20Cu10 powders occurs via a single-step, first-order transformation to a stable Zr2Pd tetragonal structure. This is in sharp contrast to the devitrification of the same amorphous alloys prepared by melt spinning, in which a primary metastable quasicrystalline phase forms. Since the mechanical milling process does not involve direct liquid phase formation of an amorphous structure, it is inferred that the short-range order in the solid state derived amorphous powder is different from that in the melt spun ribbon. © 2002 American Institute of Physics.
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81.05.Bx Metals, semimetals, and alloys
61.44.Br Quasicrystals
81.05.Kf Glasses (including metallic glasses)
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
64.70.D- Solid-liquid transitions

Large enhancement of boron solubility in silicon due to biaxial stress

Babak Sadigh, Thomas J. Lenosky, Maria-Jose Caturla, Andrew A. Quong, Lorin X. Benedict, Tomas Diaz de la Rubia, Martin M. Giles, Majeed Foad, Catalin D. Spataru, and Steven G. Louie

Appl. Phys. Lett. 80, 4738 (2002); http://dx.doi.org/10.1063/1.1484557 (3 pages) | Cited 13 times

Online Publication Date: 17 June 2002

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One of the important challenges to the semiconductor industry today is to enhance the solid solubility of several dopants, boron in particular, in silicon. We calculate the equilibrium solid solubility of boron in Si from first principles and examine the effect of biaxial stress. We find an unexpectedly large enhancement, on the order of 150%, for only 1% strain primarily due to the charge of the substitutional boron impurity in Si. We point out that this effect is an intrinsic property of Si and is expected to be important for other dopants as well. © 2002 American Institute of Physics.
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61.72.uf Ge and Si
81.05.Cy Elemental semiconductors
64.75.-g Phase equilibria
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
85.40.Ry Impurity doping, diffusion and ion implantation technology

Small band gap bowing in In1−xGaxN alloys

J. Wu, W. Walukiewicz, K. M. Yu, J. W. Ager, E. E. Haller, Hai Lu, and William J. Schaff

Appl. Phys. Lett. 80, 4741 (2002); http://dx.doi.org/10.1063/1.1489481 (3 pages) | Cited 211 times

Online Publication Date: 17 June 2002

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High-quality wurtzite-structured In-rich In1−xGaxN films (0 ⩽ x ⩽ 0.5) have been grown on sapphire substrates by molecular beam epitaxy. Their optical properties were characterized by optical absorption and photoluminescence spectroscopy. The investigation reveals that the narrow fundamental band gap for InN is near 0.8 eV and that the band gap increases with increasing Ga content. Combined with previously reported results on the Ga-rich side, the band gap versus composition plot for In1−xGaxN alloys is well fit with a bowing parameter of ∼1.4 eV. The direct band gap of the In1−xGaxN system covers a very broad spectral region ranging from near-infrared to near-ultraviolet. © 2002 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Shape of InAs quantum dots grown on the GaAs (math math math) B surface

T. Suzuki, Y. Temko, and K. Jacobi

Appl. Phys. Lett. 80, 4744 (2002); http://dx.doi.org/10.1063/1.1489087 (3 pages) | Cited 18 times

Online Publication Date: 17 June 2002

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Self-organized InAs quantum dots were grown by molecular-beam epitaxy on the GaAs (mathmathmath) B surface. Atomically-resolved scanning tunneling microscopy images were acquired in situ. Each quantum dot grows with the same orientation relative to the substrate, with mirror symmetry to the (math10) plane perpendicular to the surface, and with its central part sitting on a flat base. The shape of the central part is given by {110} and (mathmathmath) B bounding facets and a not-further-resolved round region. High-index surfaces such as (mathmathmath) B, (mathmathmath) B, and probably (mathmathmath) B are derived for the base. © 2002 American Institute of Physics.
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68.65.Hb Quantum dots (patterned in quantum wells)
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.35.B- Structure of clean surfaces (and surface reconstruction)

Thermo-piezochemistry of InAs on GaAs(001)

D. J. Bottomley

Appl. Phys. Lett. 80, 4747 (2002); http://dx.doi.org/10.1063/1.1489704 (3 pages) | Cited 5 times

Online Publication Date: 17 June 2002

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We show that the large biaxial epitaxial stress (−5.3 GPa) of InAs on GaAs(001) strongly affects the chemical reaction between elemental In and As on the GaAs(001) surface at temperatures between 200 and 500 °C. In contrast to the reaction in the bulk at zero stress, solid InAs is not the sole reaction product, but rather a mixture of elemental and compound phases including liquid In and liquid InAs result. This view differs radically from the conventional view that solid InAs is the sole stable reaction product formed at the growing surface on a GaAs(001) substrate. © 2002 American Institute of Physics.
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68.55.Nq Composition and phase identification
68.35.Dv Composition, segregation; defects and impurities
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
68.60.Bs Mechanical and acoustical properties

High frequency effective viscosities of nematic liquid crystals with tilted orientation

Arno Domack and Diethelm Johannsmann

Appl. Phys. Lett. 80, 4750 (2002); http://dx.doi.org/10.1063/1.1489705 (3 pages) | Cited 1 time

Online Publication Date: 17 June 2002

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Using quartz crystal resonators, we have measured the effective viscosities of nematic liquid crystals (LCs) in the MHz domain. The LC orientation was switched via the command-surface effect. The dependence of viscosity on orientation cannot be explained by orientational modes. They are attributed to the emission of longitudinal sound, the latter effect requiring a tilt orientation of the nematic director with respect to the surface. Optical investigations confirm the existence of a finite pretilt angle. Sensor applications are discussed. © 2002 American Institute of Physics.
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77.84.Nh Liquids, emulsions, and suspensions; liquid crystals
61.30.Eb Experimental determinations of smectic, nematic, cholesteric, and other structures
66.20.-d Viscosity of liquids; diffusive momentum transport
62.60.+v Acoustical properties of liquids
61.82.Pv Polymers, organic compounds
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